A recent meta-analysis from the Antiplatelet Trialists' Collaboration recommended that antilatelet treatment either alone or, for greater effect, in addition to other proved forms of thromboprophylaxis should be considered for patients at high risk of thromboembolism. This paper argues that the current evidence does not justify the adoption of aspirin or other antiplatelet treatment for venous thromboprophylaxis, especially when more effective alternatives exist. Furthermore, several issues relating to this latest meta-analysis need to be debated.

In a critical review Thompson and Pocock in 1991 raised an important issue of whether meta-analyses can be trusted.1 They concluded that “meta-analysis is not an exact statistical science that provides definitive simple answers to complex clinical problems. It is more appropriately viewed as a valuable objective descriptive technique, which often furnishes clear qualitative conclusions about broad treatment policies but whose quantitative results have to be interpreted cautiously.” Recently, a collaborative overview of randomised trials of antiplatelet treatment published in this journal2 came to four conclusions.

A few weeks of antiplatelet treatment roughly halved the risk both of deep vein thrombosis and of pulmonary embolism in a wide range of surgical patients (and the limited evidence in immobilised medical patients was also encouraging).

The absolute benefits seemed to be greater for those at higher risk - for example, those undergoing orthopaedic surgery.

Antiplatelet treatment can be conveniently continued after discharge from hospital (in contrast with many other forms of prophylaxis) for as long as the risk of thromboembolism remains substantial.

Antiplatelet treatment alone or, for greater effect, in addition to other proved forms of prophylaxis should be considered for patients at high risk of thromboembolism.

Our aim is to encourage constructive debate about these conclusions, taking into account the limitations of a meta-analysis. It is well established that a large number of issues …